Relay computerswhy so few 11

Vacuum tubes were not used in logic circuits until after the war. They required some modification to avoid transient errors, and of course they needed frequent replacement.

As to pricing, keep in mind that the majority of IBM's business remained in tab machines until 1962. It took a long time before electronic computers were cheap enough, esp on the low end, to fully replace tab machines. Per the other discussion, tab machines remained on site to do some offline tasks (like sorting cards) rather than do it on the CPU. Likewise, it took a long time for the Bell System to develop a cost-effective (and reliable) electronic switching telephone exchange to replace relay circuits. Here also small exchanges and PBXs were more economical to remain relay than electronic for many years.

A vaccum tube didn't run by itself, it also needed a power supply for its filament, and to be part of a circuit with resisters, diodes, and other components.

During the war the objective was to get the job done as quickly as possible. The military generally frowned upon doing stuff without immediate military payback (see Groves, "Now it can be told").

Bell Labs and Harvard (and others mentioned) developed relay machines and got them into service. Because Bell had several of them, I wonder if the design couldn't be replicated. The Harvard unit was huge and a one-time effort.